My opinion for you, Is it is all about preference it's going to come down to what YOU want. No class is better then another, Every class will have its own unique spells, And traits and it's how you use them!
I suggest we pro and con it like you said, You LOVED playing a Paladin in World Of Warcraft. Which is hard to really go in depth with because well, This isn't WoW so therefore the Paladin class may be better for you, Or different to a change you might not like. For more info on the Paladin check:
http://www.vanguardspheres.com/wiki/Paladin
Like alot of others, I love the idea of Ranger to, I've always found dashing around with my giant bow jumping off my horse and delivering a steel arrow through someones chest is always a good feeling. Where as you haven't been one before this could be an opportunity to jump on the Ranger wagon or atleast test it out! Ranger info is:
http://www.vanguardspheres.com/wiki/Ranger
And the assassin, Whoo...Guarentee there will be a large quantity of them! They are one of the coolest class ever, Who doesn't love wearing a black hood while stalking your prey? Info is:
http://www.vanguardspheres.com/wiki/Rogue
Knowing me i rambled on and didn't answer anything, Mainly because i think it will come down to what you feel, If you have to, Make all 3 and test them out for the first few levels, It's only the beginning The Only Limits Are Your Own!!!